Study is mainly concerned with assessment of factors associated with marked variation in host resistance in caries and periodontal disease. Caries studies include a comparison of caries resistant vs. susceptible adults for salivary immunologic (SIgA) and non-immunologic factors (lysozyme, lactoferrin, lactoperoxidase and aggregating substances). Other salivary proteins, such as phosphoproteins and cationic proteins (as a group), are being characterized. Periodontal disease factors are examined in a variety of ways: (a) comparative studies of saliva and plaque in heavy and light calculus formers, (b) nature of subgingival deposits, (c) nature and pathogenicity of non-adherent deposits, (d) relation of gingival fluid to clinical status, (e) antigen penetration of gingival tissues under different clinical conditions. This last study will employ a Veillonella endotoxin as the "tag" and includes fluorescent microscopy and electron microscopy in the surveillance of the marker substance.